Silicone greases of high mechanical and thermal stability



United States Patent 3,344,066 SILICONE GREASES 8F HIGH MECHANICAL AND THERMAL STABHJTY Harry M. Schiefer, John W. Vandyke, and John S. Delphenich, Midland, Mich, assignors to Dow Corning Corporation, Midland Mich, a corporation of Michigan No' Drawing. Filed Apr. 14, 1966, Ser. No. 542,459 9 Claims. (Cl. 252-28) ABSTRACT OF THE DISCLOSURE A silicone grease, the utility of which lies in a three component system for high speed bearing performance, thermal and mechanical stability; said system consisting essentially of (a) silicone fluid, (b+c) hydrophobic silica, and (d) hydroxylated siloxane fluid. An illustrative example of the grease formulation would be (a) trimethylsiloxyendblocked copolymer consisting of dimethylsiloxane units and phenylmethylsiloxane units, (b) powdered silica treated by (c) sym-trimethyltriphenylcyclotrisiloxane, and (d) phenylmethylpolysiloxane having 4.9 weight percent hydroxyl content.

This application, which is a continuation-in-part of US. application Ser. No. 447,055, filed Apr. 9, 1965 and now abandoned, relates to greases and lubricating compounds which possess stable physical properties, even when subjected to extremes of temperature and working conditions.

Greases which are made from organopolysiloxaue fluids and powdered silica thickeners are well-known.

It is the unexpected discovery of this invention that the addition of a fluid, hydroxylated organopolysiloxane plus a strongly hydrophobic, treated silica to a silicone fluid results in a grease having a significant increase in mechanical and thermal stability when compared with previously known silicone-containing greases. Many of the greases of this invention are particularly useful as lubricants for high speed bearings.

More specifically, this application relates to a grease consisting essentially of (a) 100 parts by weight of an organopolysiloxane fluid of the average unit formula R SiO where R is selected from the group consisting of monovalent hydrocarbon and haloaryl radicals of no more than 7 carbon atoms, free of aliphatic unsaturation, n has an average value of 1.9 to 2.1, the viscosity of (a) being from 20 to 30,000 cs. at 25 C.; (b) from to 25 parts of a powdered silica filler having a surface area of at least 100 square meters per gram, which filler is rendered hydrophobic by treatment with (c) from 2 to 150 weight percent, based on the weight of (b), of a compound selected from the group consisting of cyclic poysiloxanes of the formula (R' SiO) at least 50 mol percent of said R groups being methyl; silazanes of the formula S a 3-a.

where a has a value of 1 to 2; polysilazanes of the unit formula which have a viscosity of no more than 200 cs. at 25 C., and silanes of the formula R' SiX where X is chlorine, bromine, lower alkoxy, lower acyloxy, or hydroxyl, b has a value of 2 to 3, and R is in all cases as defined below; and (d) from 5 to 100 weight percent, based on the weight of (b), of a hydroxylated organopolysiloxane fluid containing an average of 1.8 to 2.1 R groups per silicon atom where R is selected from the group consisting of monovalent hydrocarbon and halohydrocarbon radicals of no more than 7 carbon atoms, said fluid having a siliconbonded hydroxyl content of at least 1 weight percent.

Ingredients (a), (b), (c), and (d) can in themselves be mixtures, if desired.

X can be any lower alkoxy radical such as methoxy, ethoxy or isobutoxy; or any lower acyloxy radical such as acetate or propionate.

R can be any monovalent hydrocarbon radical, free of aliphatic unsaturation, of no more than 7 carbon atoms, e.g. alkyl and cycloalkyl radicals such as methyl, ethyl, isopropyl, cyclopentyl, Zethylpentyl and dodecyl; and aryl radicals such as phenyl, xenyl, benzyl, and tolyl. R can also be any monovalent haloaryl radical such as chlorophenyl, dibromophenyl, and a,a,u-trifluorotolyl.

R can be any of the above examples of R, as well as any haloalkyl or halocycloalkyl radical such as ,H-chloroethyl, 3,3,3-trifluoropropyl, bromoisobutyl, cbloroallyl and dichlorocyclohexyl, as well as aliphatically unsaturated radicals such as ethynyl, allyl or cyclohexenyl.

It is preferred for R to be both methyl and phenyl. Preferred ingredients (0) are sym-trimethyltriphenylcyclotrisiloxane and hexamethyldisilazane, and a preferred ingredient (d) is a hydroxylated fluid consisting primarily of phenylmethylsiloxane units.

Ingredient (a) preferably has a viscosity of 50 to 8000 cs. at 25 C. For high speed bearing greases, the preferred maximum viscosity of (a) is 1500 cs., but higher viscosities are desirable for other uses where tacky, strongly adhering, wash-resistant greases are desired. It is frequently desirable for 5 to 15 percent of its R groups to be phenyl and the remainder methyl.

Ingredient (b) is preferably a nonstructured silica, i.e. consisting of discrete, roughly spherical particles rather than chains of particles adhering one to the other.

When (0) is a cyclotrisiloxane, the greases of this invention can be made by simply combining ingredients (a) through (d) in their proper proportions, preferably in the presence of from 0.2 to 10 mol percent, based on the moles of (b), of (e) a catalyst selected from the group consisting of ammonium hydroxide, ammonium carbo nate, NH X,

NR;,, and combinations thereof, where X is selected from the group consisting of chlorine and fluorine, R' is selected from the group consisting of hydrogen, methyl, and ethyl, and R" is selected from the group consisting of hydrogen and monovalent hydrocarbon radicals that have their valence bonds on an aliphatic carbon atom.

R can be any monovalent hydrocarbon radical as described above, e.g., methyl, isopropyl, hexyl, octadecyl, benzyl, or 2-phenylpropyl.

The preferred ingredient (e) is ammonium carbonate or ammonia. Other examples of ingredient (e) are ammonium fluoride, ammonium formate, ammonium acetate, butylamine, diisopropylamine, trimethylamine, benzyldecylamine, and cyclohexyloctadecylamine.

When (c) is a silazane, polysilazane, chlorosilane, bromosilane, or acyloxysilane, the ingredients can simply be mixed without a catalyst to obtain the improved greases of this invention. Heat treatment is often desirable to obtain the best properties.

When (c) is a silanol or an alkoxysilane, a trace of a known silanol condensation catalyst should preferably be added to the newly-formed grease while mixing, e.g. dibutyltindilaurate, tetrabutyltitanate, stannous octoate, guanidine octoate, or the catalysts listed above as ingredient (e). The mixture should also be heat-treated.

Optimum results are often obtained when ingredient (b), the silica filler, is treated with ingredients (c), (d), and, if present, ingredient (e) before mixing with ingredicut (a), the silicone fluid. This can be done by mixing ingredients (b) through (e) together in a volatile organic solvent dispersion, e.g., toluene, diethyleneglycoldimethylether, octane, or chlorobenzene, and then evaporating the solvent dispersing agent, or simply by mixing the ingredi- 5 outs themselves without a dispersing agent. Also, if desired, ingredient (d), the hydroxylated silicone fluid, can be added along with ingredient (a) to the other ingredients rather than being added first to the silica.

Generally, when the silica ingredient is being treated Example 1 To parts by weight of a powdered silica having a surface area of about 200 square meters per gram there was added 200' parts of chlorothene as a dispersing agent, 3.2 parts of a phenylmethylsiloxane fluid having approximately a 6 weight per cent hydroxyl content, 0.5 part of sym-trimethyltriphenylcyclotrisiloxane, 0.3 part of other cyclic and linear phenylmethylsiloxanes which were impurities in the ingredients, and two parts of ammonium before the addition of ingredient few hams or 10 i l i ii as heated at reflux to 150 C. forS to 10 minutes. ggi g i i ggg 3) g gg i ggz fg z zi gg ?ii zg Then 100 parts by weight of a trimethylsiloxy-endblocked render the surface of the silica hydrophobic. c-cipolymer qonslstzing 2 mol parcint {i g i- Likewise, a volatile organic solvent can be used as a 2: 3:23: ga a 3252 53 3 28 E f g igz agent during the mixing of an of the mgre' were added, and the chlorothene was removed under vacuum. ggz fig $323 2; grfemgredients (c) whlch are Opera' The product was a grease. It was tested for consistency by the test described in ASTM 1403-56T, converted as 0H; CH3 therein described to the full-scale cone penetration of s l NH ASTM D217-52T. Briefly, this test measures the depth 1 that a cone-shaped weight sinks into the grease. Low 3 2 penetration values therefore indicate a thick grease, and high values indicate a thin grease. A penetration of over 400 indicates that the material is more souplike than (13113 greaselike, whereas a penetration of less than 100 indi- (CH3 3S1NH2 SiN- cates that the grease is too thick to be normally used.

g H Penetrations were measured before and after work- I l ing the grease by forcing it through a metal plate with CH3 H 4 one millimeter holes, performed by moving the plate CH3 CH3 0 through the grease. The working test consists of 60 onel t m It second strokes of the plate. O f H K M CHBCHZTWCCHM The bleed and evaporation rates of the grease were CH3 measured in terms of weight loss of the grease. phenyldimethylsilanol, and dimethyldichlorosilane. The results were:

Penetration Penetration after 24 hrs. at Bleed after Evaporation 400 F. 30 hrs. at after 22 hrs. Grease 400 F at 400 F. Unworked Worked Unworked Worked (percent) (percent) (a) The above grease 279 297 249 286 9. 22 2. (b) A commercial soap-thickened silicone grease..- 283 297 95 219 5-10 5-;3

It is preferred for ingredient (d) to be incompatible The above two greases were tested in an M.R.C. Sl7, with ingredient (a). The best bearing performance is size 204 bearing in accordance with Federal Standard 791, obtained under those circumstances. Method 333. The bearing was run at 10,000 r.p.m. under The term incompatible is defined to mean the folv a load of 5 lbs. and a temperature of 450 F. lowing: if 2 parts by weight of a given ingredient (d) 95 The bearing with grease (a) ran for over 1000 hours cannot dissolve in 10 parts by weight of an ingredient without failing, while the bearing with grease (b) failed in (a) to form a one phase solution rather than an emulsion less than 24 hours. or a suspension, that ingredient (d) is incompatible with Example 2 g g iigi g gil' gggg are companble If they are (a) Another batch of grease was made by the method When ingredient (d) is compatible with ingredient (a), 25 3221 5 52 3?: 2335 was used In Place of greases with high mechanical stability result, but their (b) A r a p d n mechanical stability at high temperatures is generally ing ease 5 ma 6 m e 0 m to sufiicient for them to exhibit superior performance in high 100 parts by Welght 0f a powdered silica havmg a Surspeed bearings. face area of 400 square meters per gram, there was added other additives Such as corrosion and oxidation 27.5 parts of sym-trimethyltriphenylcyclotrisiloxane and hibitors, dyes, bleed reducing agents, etc can be added to one part of ammonium carbonate. ThlS was rolled at room the compositions of this invention without departing from temperature for 5 days i heated, at 150 the scope of the claims. vacuum to remove all remaining ammonia. A hydrophobic The greases of this invention tend to have higher extrudslhca was recovered ability than other silicone greases of similar physical con- To Parts by Weight of the abflve tfeatfid Silica there Sistency was added 81.9 parts of a trimethylsiioxy-endblocked poly- The following examples are illustrative only and should SiIOXaIlB 601101301161 Consisting of mol Percent Of nut be o tr ed a li iting th i v ti hi h is methylsiloxane units and 7.5 mol percent of phenylmethylproperly delineated in the appended claims.

siloxane units, having a viscosity of 1000 cs. at 25 C.

To 9 parts by weight of a powdered silica having a Surface area of 200 square meters per gram there was added 100 parts of a blend of dimethylpolysiloxane fluids, the blend having a viscosity of 6000 cs. at 25 C. This Was milled until a grease was formed.

These greases were tested as in Example 1:

. 6 (d) To 100 parts by weight of a powdered silica having a surface area of 400 square meters per gram, there was added 18 parts of sym-triphenyltrimethylcyclotrisiloxane and one part orf ammonium carbonate. The mixture was rolled for one day at room temperature and allowed Pentration Penetration after 24 hrs. at 400 F. Bleed after 30 Evaporation Grease hrs. at 400 F. after 22 hrs. at

(percent) 400 F. (percent) Unworked Worked Unworked Worked Sample (a) 279 90 272 286 12. 7 1. Sample (1)) 256 Sample (c) 212 A fourth grease (d) was prepared from 86.5 weight percent of a dimethylpolysiloxane fluid with a viscosity of about 500 cs. at 25 C., 10.3 percent of powdered silica filler with a surface area of over 100 m. /gm., 2.7 percent of a hydroxylated methylpolysiloxane fluid, having a hydroxyl content of about 4 weight percent, 0.36 percent of boric acid and 0.14 percent of pentaerythritol, the latter two ingredients being known silicone grease stabilizers.

Grease (d), and grease (a), were both tested in the bearing test of Example 1.

The bearing with grease (a) operated for over 1040 hours without failing, while the bearing with grease (d) failed in less than 24 hours.

Grease (a) is within the scope of the claims of this application. Greases (b), (c), and (d) are outside of the scope of the claims of this application, being included to show the superiority of grease (a).

Example 3 (a) To 14.4 parts by weight of the treated silica of Example 2(b) there was added 84.4 parts by weight of a trimethylsiloxy endblocked copolymer consisting of 92.5 mol percent of dimethylsiloxane units and 7.5 mol percent of phenylmethylsiloxane units, having a viscosity of 1000 cs. at 25 C., plus 1.1 parts of a phenylmethylpolysiloxane fluid having a 4.9 weight percent hydroxyl content. The milled composition was a grease.

to stand for 2 more days, and then heated at 150 C. in a vacuum to remove all ammonia.

12.5 parts by weight of this treated filler were milled with 80 parts of a trimethylsiloxy endblocked dimethylpolysiloxane having a viscosity of 100 cs. at 25 C. and 2.8 parts of a methylpolysiloxane fluid having a 4.15 weight percent hydroxyl content. The product was a grease.

(e) 9.3 parts by weight of the treated silica of (d) above that had been heated immediately after the one day of rolling were milled with 87.9 parts of the siloxane copolymer of (c) above and 2.8 parts of diphenylsilanediol. A grease was formed.

(f) To 100 parts by weight of powdered silica having a surface area of 400 square meters per gram, there was added 15 parts of hexamethylcyclotrisiloxane and one part of ammonium carbonate. This was rolled for 24 hours at room temperature, and then heated at 150 C. to drive off all the ammonia.

To 15.9 parts by weight of this treated silica, there were added 81.2 parts of a trimethylsiloxy endblocked dimethylpolysiloxane fluid having a viscosity of 1000 cs. at 25 C. and 2.9 parts of a hydroxylated dimethylpolysiloxane fluid having a 3.9 weight percent hydroxyl content.

The above greases, which were within the scope of the claims of this application, Were tested as in Example 1.

Penetration Penetration after 24 hrs. at Bleed after 30 Evaporation 400 F. hrs. at 400 F. after 22 hrs. Grease (percent) at 400 F. Unworked Worked Unworked Worked (percent) 242 275 230 313 1. 48 252 275 230 297 2. 23 2: i2 260 267 242 294 7. 1. 00 301 346 238 368 5. 86 4. 57 338 387 313 353 14. 2. 97 272 279 193 331 not measured not measured (b) To 13.7 parts by weight of the treated silica of 55 Example 4 g. of a phenylmethylpolysiloxane fluid having a hydroxyl content of about 6 weight percent, 2 g. of sym-triphenyltrimethylcyclotrisiloxane, about 1.6 g. of other cyclic and linear phenylmethylsiloxane polymers which were added as impurities and 1 g. of ammonium carbonate. This mixture was rolled and heated at 50 C. for 44 hours. The mixture was then heated at 150 C. in a vacuum to remove all ammonia.

To 17.7 parts by weight of the above treated silica there was added 82.3 parts of a trimethylsiloxy endblocked copolymer consisting of 92.5 mol percent of dimethylsiloxane units and 7.5 mol percent of phenylmethylsiloxane units, having a viscosity of 100 cs. Upon milling a grease was formed.

When 100 parts by Weight of (a) an organopolysiloxane fluid consisting essentially of 75 mol percent of dimethylsiloxane units, 20 mol percent of cyclohexylmethylsiloxane units, and 5 mol percent of dibromophenylmethylsiloxane units, having a viscosity of 20,000 cs. at

. 25 C., are milled with (b) 7 parts of silica having a surface area of 400 square meters per gram, (c) 1 part of tris 3,3,3-trifluoropropyltrimethylcyclotrisiloxane, (d) 5 parts of a fluid 3,3,3-trifluoropropylmethylpolysiloxane having a 3 weight percent hydroxyl content, and (e) 0.5 part of concentrated ammonium hydroxide, a stable grease is formed.

Example 5 When 100 parts by weight of (a) an organopolysiloxane fluid consisting of mol percent of dimethylsiloxane units and 5 mol percent of chlorophenyhnethy1- siloxane units, having a viscosity of 1500 cs. at 25 C.,

7 are milled with (b) parts by weight of silica having a surface area of 100 square meters per gram, (c) 1 part of trihexyltrimethylcyclotrisiloxane, (d) 1 part of a fluid propylphenylpolysiloxane having a 3 weight percent hydroxyl content, and (e) 2 parts of n-propylamine, a stable grease is formed.

Example 6 When 100 parts by weight of (a) an equal weight blend of copolymers of 10 mol percent of diphenylsiloxane and 90 mol percent of dimethylsiloxane having viscosities of 20,000 cs. and 1,000 cs. respectively, measured at 25 C., (b) 10 parts of the treated silica filler of Example 3(d), and (c) 1 part of a fluid 2-phenylpropylmethylpolysiloxane having a 3.5 weight percent hydroxyl content are milled, a stable grease is formed.

Example 7 (a) To 20 parts by weight of a powdered silica having a surface area of about 400 square meters per gram, there was added (1) 300 parts of chlorothene,

(2) 2 parts of a mixture consisting of 80 weight percent of a phenylrnethylsiloxane fluid having approximately a 6 weight percent hydroxyl content, 12.5 percent of sym-trimethyltriphenylcyclotrisiloxane, and 7.5 percent of other cyclic and linear phenylmethylsiloxane impurities, and

(3) 2 parts of hexamethyldisilazane.

8 This was mixed and then heated at 150 C. with agitation for one-half hour under a vacuum, resulting in a hydrophobic silica.

To the resulting product there was added This was milled until a grease was formed.

(b) To 21 parts by weight of a powdered silica having a surface area of about 200 square meters per gram and having one part of water added thereto, there was added (1) 300 parts of chlorothene,

(2) A total of 3 parts of the mixture of ingredient (2) in experiment (a) above, and

(3) 15 parts of hexamethyldisilazane.

This composition was mixed and heated as in (a) above, creating a hydrophobic silica, and 115 parts by weight of the similar organopolysiloxane copoly'rner as in (a) above, having a viscosity of cs. at 25 C., was added with stirring and milling along with the same amounts of ingredients (5) and (6) as above, until a grease was formed.

The properties of the two greases were tested as in Example 1:

Penetration Penetration alter 72 hrs. at 200 C. Evap. after Bleed after Grease 400 2% hzs. at- 0 450 310 hrs. at t Bearing life Unworked Worked Unworked Worked Ween (pemn (hows) (u) 238 272 252 309 1. 03 5. 14. 639 (b) 242 56 219 286 2. 15 5. 82 Over 800 Example 8 The following compositions were prepared:

Composition Silica having surface area Ohlorothene Ingredient (2) of 3 ts. b wt. of that 11 'l of 400 lg mp p y o owing s1 azane i (a) 20 pts. by wt 300 pts. by wt 3 pts. by wt CH =CHSi NH C 3 2 a (b) 20 pts. by wt 300 pts. by wt 3 pts. by wt CF CH CH2Si NH C 3 2 (c) 20 pts. by Wt 300 pts. by wt 3 pts. by wt 13 wt. percent of:

3 wt. percent of hexane.

These compositions were each mixed and heated as in Example 7(a), resulting in a hydrophobic silica, and to each there was added the trimethylsiloxy-endblocked copolymer of Example 7(a), to compositions (a) there was 10 This hydrophobic silica was then milled into 89.4 parts by weight of the siloxane copolymer of Example 7(a) plus 1 part of the mixture of ingredient (2) of Example 7(a).

The product was a grease having the following propadded 115 parts by weight; to composition (11) 130 parts; 5 erties, measured as in Example 1.

Penetration i t iiio iii 72 hrs- Bleed after 30 Evap. after 22 Composition hrs. at 450 F. hrs. at 400 F.

(percent) (percent) Uuworked Worked Unworked Worked and to composition 145 parts. The same amounts of Penetration: ingredients and (6) as in Example 7 were also added Ik d 283 to each composition. Upon milling, a grease was formed W k d 297 in each case' Penetration after 72 hrs. at 200 C.:

The properties of each of these greases were tested as in Unworked 212 Example 1: Worked 272 Example 9 Bleed after 30 hrs. at 450 F. (percent) 6.26 When 100 parts of tolyldimethyl-endblocked phenyl- P- after 22 hrs-B1430) (P t) 2.89 methylpolysiloxane having a viscosity of 5000 cs. at 25 Example 12 C. are milled with (a) 10 g. of a silica powder having a surface area of about 300 m. /g. and which has been rendered hydrophobic by treatment with 2 g. of octamethylcyclotetrasilazane and (b) 2 g. of

i 810 HO H (3H2 CHgCdTt 2 a mechanically and thermally stable grease which is suitable for use in ahigh -speed bearing results.

Example 10 To about 10.5 parts by weight of silica having a sur face area in excess of 100 square meters per gram there was added about 1 part of phenyldimethylsilylamine.

I This was shaken for a few minutes until the silica was rendered hydrophobic.

This hydrophobic silica was then milled into 86.4 parts by weight of a trimethylsiloxy-endblocked copolymer of 92.5 mol percent dimethylsiloxane units and 7.5 mol percent phenylmethylsiloxane units, having a viscosity of 200 cs. at 25 C., plus 3.1 parts of OH; HO S iO CHzCFa -a The product was a grease having the following properties, measured as in Example 1.

Penetration:

Unworked 267 Worked 279 Penetration after 24 hrs. at 200 C.:

Unworked 219 Worked -2 275 Bleed after hrs. at 450 F. (percent) 5.83 Evap. after 22 hrs. at 400 F. (percent) 2.30

Example 11 T0 about 9.6 parts by weight of a silica having a surface area in excess of 100 square meters per gram, there was added about 1 part of phenylmethyldimethoxysilane. This was rolled at 100 C. until a hydrophobic silica resulted.

When 20 g. of finely divided silica having a surface area of 300 m. g. are treated with 2 g. of any of the following hydrophobing agents so as to render the silica hydrophobic, and the treated silica is milled with 200 g. of

greases which are suitable as high speed bearing greases result:

( CH3) aSiCl OtHn) 810 071215, plus a trace of dibutyltindilaurate Si(OH) plus 0.2 g. of guanidine octoate 2 H C FsCHzcHa luo 0 C 3)! (CH3)3S1OH plus 0.1g. oi dibutylamine NH2 SiN Example 13 To 92.5 parts by weight of a trimethylsiloxy-endblocked copolymer of 92.5 mol percent dimethylsiloxane units and 7.5 mol percent phenylmethylsiloxane units having a viscosity of 1000 cs. at 25 C., there was added 5.5 parts of a finely-divided silica which was reacted with more than 2 percent of its weight of trimethylchlorosilane, rendering it hydrophobic, and 2 parts of a fluid dimethylpolysiloxane which had a hydr-oxyl content of 3.8 weight percent.

This was milled into a grease which was tested as in Example 1:

Penetration after heating 2%. hours at 550 F.:

Unworked Worked The unworked and worked penetrations before heating were in the vicinity of 290.

The same formulation, absent the hydroxylated dimethylpolysiloxaue, had an unmeasurable unworked penetration after heating for 2% hours at 550 F., the grease being lumpy and hard.

Example 14 To 14.0 parts by weight of a powdered silica having a surface area of about 400 square meters per gram, as determined by known techniques of adsorption of nitrogen, there was added 2.1 parts of [(Ql l This was shaken until it was hydrophobic, and then it was milled with 80.7 parts by weight of a diphenylmethylsiloxane-endblocked phenylmethylpolysiloxane having a viscosity at C. of 600 es, and 3.2 parts of a dimethylr polysiloxane having a hydroxyl content of 3.2 weight percent.

The product was a grease having the following properties, as tested in Example 1:

Bleed after hrs. at 450 F percent 1.98 Evaporation after 22 hrs. at 400 F do 2.10 Penetration before heating:

Unworked 249 Worked 33 l Penetration after 72 hrs. at 400 F.:

Unworked 189 Worked 309 Example 15 Penetration:

Unworked 301 Worked 357 Penetration after 72 hrs. at 400 F:

Unworked 208 Worked 368 Bleed after 30 hrs. at 450 F percent 2.32 Evap. after 22 hrs. at 400 F do 1.53

The grease was subjected to the bearing test of Example 1, and lasted for 631 hours.

Example 16 A blend of 60 parts by weight of dimethylpolysiloxane having a viscosity of 30,000 cs. at 25 C. plus 36 parts of a dimethylpolysiloxane having a viscosity of 500 cs.

12 at 25 C. (the blend having a viscosity of about 5000 cs. at the same temperature) was mixed with 4 parts of the mixture of ingredient (2) of Example 7(a) and 8 parts of powdered silica having a surface area of about 200 m. /g.

The mixture was heated in a vacuum oven for 2 hours at 150 C. to form a grease having an unworked penetration of 204, a worked penetration of 242, and, after 24 hours at 200 C., no bleed and 1.28 weight percent of evaporation, determined as in Example 1.

The product was an excellent lubricating compound, being long-lasting and stable in the presence of pressurized steam.

That which is claimed is:

1. A grease consisting essentially of (a) 100 parts by weight of an organopolysiloxane fluid of the average unit formula R SiO where R is selected from the group consisting of monovalent hydrocarbon and haloaryl radicals of no more than 7 carbon atoms and free of aliphatic unsaturation, n has an average value of 1.9 to 2.1, the viscosity of (a) being from 20 to 30,000 cs. at 25 C.;

(b) from 5 to 25 parts of a powdered silica filler having a surface area of at least 100 square meters per gram, which filler is rendered hydrophobic by treatment with (c) from 2 to 150 weight percent, based on the weight of (b), of a compound selected from the group consisting of cyclic polysiloxanes of the formula (R' SiO) at least 50 mol percent of said R groups being methyl; silazanes of the formula (R's a S-a where a has a value of 1 to 2; polysilazanes of the unit formula which have a viscosity of no more than 200 es. and silanes of the formula R' SiX where X is chlorine, bromine, lower alkoxy, lower acyloxy, or hydroxyl, b has a value of 2 to 3, and R is in all cases as defined below; and

(d) trom 5 to 100 weight percent, based on the weight of (b), of a hydroxylated organopolysiloxane fluid containing an average of 1.8 to 2.1 R groups per silicon atom, where R' is selected from the group consisting of hydrocarbon and halohydrocarbon radicals of no more than 7 carbon atoms, having a silicon-bonded hydroxyl content of at least 1 weight percent.

2. The grease of claim 1 where the R groups of ingredient (a) are from 2 to 15 mol percent phenyl and from to 98 mol percent methyl.

3. The grease of claim 1 where ingredient (a) is essentially dimethylpolysiloxane.

4. The grease of claim 1 where ingredient (c) is hexamethyldisilazane.

5. The grease of claim 1 where ingredient (d) consists essentially of a hydroxylated phenylmethylpolysiloxane.

6. The grease of claim 1 where (a) has a viscosity of from 50 to 1500 cs. at 25 C.

7. A grease consisting essentially of (a) 100 parts by weight of an organopolysiloxane fluid of the average unit formula R SiO where R is selected from the group consisting of monovalent hydrocarbon and halohydrocarbon radicals of no more than 7 carbon atoms, free of aliphatic unsaturation, at least 85 percent of said R groups being methyl, and n has an average value of 1.95 to 2.1,

13 the viscosity of (a) being from to 15,000 cs. at C.; from 5 to 25 parts of (b) a powdered silica filler having a surface area of at least 100 square meters per gram; from 2 to weight percent, based on the weight of (b), of (c) a cyclic siloxane of the formula (R SiO) at least mol percent of said R groups being methyl; and from 5 to weight percent, based on the weight of (b), of (d) a hydroxylated organopolysiloxane containing an average of 1.8 to 2.1 R groups per silicon atom, R being defined above, and a silicon-bonded hydroxyl content of at least 2 weight percent. 8. The grease of claim 7 where (c) is syrntriphenyltrimethylcyclotrisiloxane.

9. The grease of claim 1 where (d) is incompatible with (a).

References Cited UNITED STATES PATENTS 2,951,862 9/1960 Pierce 25249.6 2,985,679 5/1961 Pepe 25249.6 3,045,036 7/ 1962 Jex et al 25249.6 3,061,545 10/1962 Badger 252-49.6 3,112,332 11/1963 Pike 25249.6 3,145,175 8/1964 Wright 25249.6 3,145,225 8/1964 Brown 25249.6 3,171,851 3/1965 Pepe 25249.6 3,174,987 3/ 1965 Simmler et al. 25249.6 3,192,157 6/1965 Gowdy 25249.6 3,278,435 10/ 1966 Kawahora 25249.6

DANIEL E. WYMAN, Primary Examiner.

I. VAUGHN, Assistant Examiner. 

1. A GREASE CONSISTING ESSENTIALLY OF (A) 100 PARTS BY WEIGHT OF AN ORGANOPOLYSILOXANE FLUID OF THE AVERAGE UNIT FORMULA RNSIO4-N/2 WHERE R IS SELECTED FROM THE GROUP CONSISTING OF MONOVALENT HYDROCARBON AND HALOARLY RADICALS OF NO MORE THAN 7 CARBON ATOMS AND FREE OF ALIPHATIC UNSATURATION, N HAS AN AVERAGE VALUE OF 1.9 TO 2.1, THE VISCOSITY OF (A) BEING FROM 20 TO 30,000 CS. AT 25*C.; (B) FROM 5 TO 25 PARTS OF A POWDERED SILICA FILLER HAVING A SURFACE AREA OF AT LEAST 100 SQUARE METERS PER GRAM, WHICH FILLER IS RENDERED HYDROPHOBIC BY TREATMENT WITH (C) FROM 2 TO 150 WEIGHT PERCENT, BASED ON THE WEIGHT OF (B), OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF CYCLIC POLYSILOXANES OF THE FORMULA (R''2SIO)3, AT LEAST 50 MOL PERCENT OF SAID R'' GROUPS BEING METHYL; SILAZANES OF THE FORMULA 